1. Field of the Invention
The present invention relates to the removal of solvents, such as hexane and the like, from flakes such as soybean flakes or cottonseed flakes or other oil bearing seeds, nut, animal tissue etc. The invention relates more particularly to a drainer-conveyor for transferring spent flakes from a solvent extraction apparatus to a desolventizer-toaster apparatus in a flake material processing system.
2. Prior Art
It is known to use a screw-type or en masse continuous chain conveyor to transfer the spent flakes coming from the lower portion of a solvent extraction apparatus to a desolventizer-toaster apparatus for subsequent processing to remove the solvent from the flakes which was picked up in the solvent extraction process. It is also known to provide a drainer section in the conveyor in order to permit the solvent to drain from the flakes as it is passing from the solvent extraction apparatus to the desolventizing toaster apparatus. It is advantageous to remove as much solvent as possible from the flakes prior to their entering the desolventizer-toaster apparatus so that less energy is required to evaporate the solvent and remove it from the flakes during processing in the desolventizer-toaster apparatus, prior to its subsequent processing.
In order to enhance the drainage of solvent from the flakes in the drainer section of the conveyor extending from the solvent extraction apparatus to the desolventizer-toaster apparatus, a negative pressure or vacuum has been applied to the drainer section of the conveyor to attempt to draw out additional solvent prior to passing the flakes into the desolventizer-toaster. A difficulty encountered, however, is that unless a solid mass of flakes is maintained in the conveyor from the drainer section towards the desolventizer-toaster as well as towards the solvent extraction apparatus, the negative pressure tends to draw solvent and moisture from either of these apparatus back into the flakes thus defeating the purpose and advantage of the drainer section in reducing the solvent that needs to be removed in the desolventizer-toaster. The occurrence of openings passing through the conveyors is random and not continuous and as a result produces nonuniformity in the removal of solvent. In order to overcome this problem it is necessary to maintain a certain level of flakes in the collecting trough beneath the solvent extraction apparatus and, likewise, to maintain a blockage or complete filling of the conveyor from the drainer section to the desolventizer-toaster.